iStockphoto/Thinkstock(EXETER, N.H.) -- The New Hampshire hospital lab technician, charged by authorities for causing a Hepatitis C outbreak that infected 31 patients, will plead guilty. David Kwiatkowski, 32, was arrested and charged with acquiring a controlled substance by fraud and tampering with a consumer product with "reckless disregard" for the risk of others, according to an affidavit filed in U.S. District Court for the District of New Hampshire. He was caught in a scheme in which he stole patients' drugs, then replaced the contents of their syringes with saline.

But since Kwiatkowski tested positive for Hepatitis C in June 2010, he passed it on to the hospital patients who were injected with his used, saline-filled syringes, according to the affidavit.

"If he knew that he was infected and he put those needles back on the shelf, that is the definition of evil," Dr. Richard Besser, ABC News' chief health and medical editor, told Good Morning America last summer. "Anyone who was in those hospitals when he was working there is potentially at risk. We're talking tens of thousands of people."

Hepatitis C is a liver disease that can last a few weeks or for the rest of the patient's life, according to the Centers for Disease Control and Prevention. The virus is spread through the blood, and there is no vaccine. Symptoms include vomiting, abdominal pain, and jaundice.

"The evidence gathered to date points irrefutably to Kwiatkowski as the source of the Hepatitis C outbreak at Exeter Hospital," U.S. Attorney John P. Kacavas said in a news release at the time of Kwiatkowski's arrest. "With his arrest, we have eliminated the 'serial infector' posed to public and health safety."

Kwiatkowski was indicted in November on seven counts of acquiring a controlled substance by fraud and seven counts of tampering with a consumer product, according to a news release. Acquiring a controlled substance by fraud is punishable by up to four years in prison for each count, and tampering with a consumer product is punishable by up to 10 years in prison for each count.

"You go under and you wake up hours later and you don't know who was around you," a former patient told the Boston Herald on condition of anonymity last summer. "I'm scared. I have no idea who was around me when I was under and unfortunately, I was there three different times."

The plea hearing is scheduled for 9:30 a.m. Wednesday.

Assistant United States Attorney John Farley, who is prosecuting the case, declined to comment.